1. Field of the Invention
The present invention generally relates to a method for supporting a thinned wafer. More particularly, the present invention relates to a method for supporting a thinned wafer with a eutectic bonding carrier.
2. Description of the Prior Art
Wafer backside grinding (BSG) is conventionally employed to reduce the original thickness of a semiconductor wafer after the device fabrication and passivation. The profile of a wafer is reduced to a thickness suitable for assembling dies (obtained after a wafer singulation step) on substrate packages.
For some specific products, such as power ICs or MOSFETs, the wafer will be grinded to an ultra-thin dimension (ex. lower than 100 μm). Specific technologies are required to perform backside grinding to such an extreme scale. The current approach is to adhere the wafer to be grinded on a supporting carrier via an adhesive tape or glue. However, all currently available adhesive can't withstand high temperatures. For example, when the wafer is processed at a temperature higher than 400° C., the adhesive will deteriorate and won't be able to be properly removed. For this reason, wafers using the adhesive method can only be processed at low temperatures, such as in etching processes, physical vapor deposition (PVD) processes, or chemical vapor deposition (CVD) processes, which usually process at temperatures lower than 300° C.
Another approach to solve this problem is the so-called TAIKO process developed by DISCO. This process leaves an edge (approximately 3 mm) on the outermost circumference of the wafer and grinds only the inner circumference of the wafer to an ultra-thin scale. Using this method may lower the risks in thin wafer handling and potential warpage issues. However, in the TAIKO process, a specific edge ring device is required to hold and support the thinned wafer during the whole process flow. This may imply that all of the process tools, including WAT/testing tools, need to be modified to fit to this kind of technology. Moreover, since the wafer is held by an edge ring in the TAIKO process, the wafer center is very vulnerable to damage and may be easily broken, especially in the testing step, which the probes of testing tools are usually applied from the topside and backside of the wafer respectively.
Accordingly, it is still necessary to provide a novel method and structure for holding and processing the above-mentioned extremely thinned wafer.